1. Field of the Invention
This invention relates to Josephson device parametrons, and more particularly to these parametrons and their use in various circuit configurations.
2. Description of the Prior Art
Josephson tunneling devices are known in the art and have been used previously in memory type circuitry. For instance, U.S. Pat. No. 3,625,583 describes a memory and storage system using superconducting Josephson tunneling devices for current steering in a plurality of memory cells. In addition, detection of the currents in each memory cell is achieved through the use of additional Josephson tunneling devices whose voltage state is determined by the currents in the associated memory cells.
The prior art circuits employing Josephson tunneling devices used these devices in pulse-type modes of operation. That is, information was represented by the presence and absence of voltage or current signals, or by the direction of currents in the circuit. The prior art has not addressed the use of Josephson tunneling devices in other types of operation which may be advantageous.
The prior art has also not addressed the problem of interconnections between circuit chips having circuits thereon for memory and logic functions. Such functions could be performed by Josephson tunneling devices or by other electrical components. In general, the particular electronic components used are made as small as possible. This leads to a problem in providing interconnecting wires between modules located on the same circuit chip and between different circuit chips.
In the present invention, a new type of operation for Josephson tunneling devices is presented. An isolated Josepshon tunneling device (i.e., one which is not provided with voltage or current connections) functions as a parametron which can be excited into oscillation by an applied magnetic field. The isolated junction oscillates with either of two stable phases at a frequency .omega. simply by varying the magnetic field (pump) at a frequency 2.omega.. The phase into which the device locks itself is determined by a small injected control signal having the desired phase. In another arrangement, pump frequencies different than 2.omega. are used in a Josephson tunneling parametron comprised of connected parallel junctions.
Parametric circuits using Josephson tunneling devices have been proposed previously. However, these circuits used the Josephson tunneling device as a component in a conventional circuit (i.e., one using standard components and bias source). No where is it shown that an isolated Josephson tunneling device can itself function as a parametron. Examples of the prior art concerning parametric amplification using Josephson tunneling devices are the following:
H. zimmer, APPLIED PHYSICS LETTERS, 10, 193, Apr. 1, 1967; PA1 Kanter et al, APPLIED PHYSICS LETTERS, Vol. 19, No. 12, Page 515, December 1971.
Classical parametrons have limited gain since the resonant frequency .omega. can only be varied by small amounts. In contrast with this, the isolated Josephson tunneling device parametrons of the present invention may achieve gains of 5,000--10,000 in only 10 oscillations, since the change in frequency .omega. in a Josephson junction is very large for even moderate changes of pump magnetic field. Further, whereas classical parametrons did not perform at very high frequencies, (10.sup.11 -10.sup.12 Hz), the present Josephson tunneling device parametrons will perform at these frequencies.
Accordingly, it is the primary object of this invention to provide a new type of parametron which has high gain and performs at very high frequencies.
It is another object of this invention to provide improved circuitry for connecting modules and circuit chips using a minimum number of interconnections. It is still another object of this invention to provide a superconducting parametron which does not require current or voltage inputs for parametric operations.
It is a still further object of this invention to provide an improved means for communication between circuit chips using a minimum number of interconnections.
It is another object of this invention to provide parametric circuitry using Josephson tunneling device parametrons.
It is still another object of this invention to provide apparatus for transferring pulse-type information to information represented by the phase of an AC signal, and vice versa.